High porosity abrasive articles and methods of manufacturing same

ABSTRACT

An abrasive article includes a polymer matrix and abrasive grains dispersed in the polymer matrix, wherein the abrasive article has a void volume of at least 50%. The polymer matrix is polymerized from a monomer including at least one double bond.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is a divisional of U.S. Patent Application No.12/372,549, filed Feb. 17, 2009, entitled “HIGH POROSITY ABRASIVEARTICLES AND METHODS OF MANUFACTURING SAME” naming Inventors RachanaUpadhyay and Richard Hall, which in turn claims priority from U.S.Provisional Patent Application No. 61/046,134, filed Apr. 18, 2008,entitled “HIGH POROSITY ABRASIVE ARTICLES AND METHODS OF MANUFACTURINGSAME,” naming inventors Rachana Upadhyay and Richard Hall, whichapplication is incorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

This disclosure, in general, relates to high porosity abrasive articlesand methods for making such high porosity abrasive articles.

BACKGROUND

Abrasive articles are used in various industries to machine work pieces,such as by lapping, abrading, or polishing. Machining utilizing abrasivearticles spans a wide industrial scope from the optics industry, theautomotive body repair industry, to the semiconductor fabricationindustry. In each of these examples, abrasives are used to remove bulkmaterial or affect surface characteristics of products or work pieces.

In a particular example, the semiconductor industry uses abrasivearticles to remove bulk material from the backside of a semiconductorwafer, known as backgrinding. Backgrinding often includes multiplemachining steps, including a coarse grind to effect bulk materialremoval, followed by one or more fine grind steps to reduce subsurfacedamage, and provide a smooth surface finish that may be within a rangeof 50 to 500 Angstroms, for example. Such processing is believed toresult in more consistent electrical properties in the substrate of thecircuits printed on the front side of the semiconductor wafer. Moreover,with the advent of technologies that rely on the formation of electricalconnections through the wafer, backside planarization, bulk materialremoval, and surface quality are becoming increasingly important.

However, the bulk material removal rate and the surface quality of thebackside of the semiconductor wafer are notably dependent on not onlythe grit size of the abrasive article used in machining, but also onstructure of the abrasive article. In particular, abrasive articles thattrap dislodged abrasive grains and swarf between the abrasive articleand the wafer often cause scratching in the surface of the wafer. Assuch, the surface quality on the backside of the wafer is poor followingabrasion, which may influence the electrical properties and thecircuitries formed on the front side of the wafer.

As such, an improved abrasive article would be desirable.

SUMMARY

In a particular embodiment, an abrasive article includes a polymermatrix and abrasive grains dispersed in the polymer matrix. The polymermatrix is polymerized from a monomer including at least one double bond.The abrasive article has a void volume of at least 50%, such as at least65%. In a particular example, the abrasive grains have an averageparticle size of 0.1 μm to 100 μm, such as 0.1 μm to 10 μm. In anotherparticular example, the abrasive grains are selected from the groupconsisting of silica, alumina, zirconia, zirconia/alumina oxides,silicon carbide, garnet, diamond, cubic boron nitride, silicon nitride,ceria, titanium dioxide, titanium diboride, boron carbide, tin oxide,tungsten carbide, titanium carbide, iron oxide, chromia, flint, andemery. For example, the abrasive grains may be superabrasive grainsselected from the group consisting of cubic boron nitride, hardcarbonaceous materials and a mixture thereof. In a further example, theabrasive grains have a Mohs hardness of at least 8. In a particularexample, the abrasive article includes greater than 10 wt % of theabrasive grains. In another particular example, the abrasive articleincludes 2 vol % to 30 vol % of the abrasive grains. In an exemplarycase, the polymer matrix includes a polymer formed of a monomer selectedfrom the group consisting of vinyl, acrylate, methacrylate, conjugateddiolefin, allene, and olefin halide monomers. In another example, thepolymer matrix has an open cell structure, such as an open cellstructure having a pore and throat configuration. Further, the abrasivearticle may have a surface area of at least 2.0 m²/g, such as at least3.0 m²/g.

In another exemplary embodiment, a method of forming an abrasive articleincludes combining polymeric precursors and abrasive grains to form afirst liquid component, forming an emulsion from the first liquidcomponent and a second liquid component, and curing the polymericprecursors of the first liquid component. The second liquid component issubstantially immiscible with the first liquid component. The polymerprecursors include a monomer including at least one double bond. In anexample, combining the polymer precursors and the abrasive grainsincludes combining an emulsifier with the polymer precursors and theabrasive grains. In an additional example, combining the polymerprecursors and the abrasive grains includes combining a stabilizingagent. In a particular example, curing comprises exposing the emulsionto actinic radiation or thermal energy. In another particular example,forming the emulsion includes forming the emulsion with at least 65 vol% of the second liquid component. In an additional example, the methodfurther includes treating the abrasive grains with a coupling agent. Ina particular example, the coupling agent is hydrophobic. In a furtherparticular example, the polymer precursors are thermally curable. Inanother particular example, the polymer precursors are polymerizablethrough free radical polymerization. In particular, the first liquidcomponent may be hydrophobic. In an example, combining the polymerprecursors and the abrasive grains includes combining at least 10 wt %of the abrasive grains. In a further example, the abrasive grains havean average particle size of 0.5 μm to 6 μm.

In an additional exemplary embodiment, a method of polishing an articleincludes applying an abrasive article to the surface of the article andabrading the surface of the article. The abrasive article includes apolymer matrix and abrasive grains dispersed in the polymer matrix. Thepolymer matrix is polymerized from a monomer including at least onedouble bond. The abrasive article has a void volume of at least 50 vol%, such as at least 65 vol %. In an example, the abrasive articleincludes greater than 10 wt % of the abrasive grains.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousfeatures and advantages made apparent to those skilled in the art byreferencing the accompanying drawings.

FIG. 1 includes an illustration of an open cell structure exhibiting apore and throat configuration.

FIG. 2 and FIG. 3 include graphs illustrating the wear rate of samples.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DESCRIPTION OF THE DRAWINGS

In a particular embodiment, an abrasive article includes a polymermatrix and abrasive grains dispersed within the polymer matrix. Theabrasive article has a void volume of at least 50 vol %. In a particularexample, the abrasive article has an open cell structure in which thevoid space exhibits a pore and throat configuration. In an example, theabrasive grains have an average particle size of at least 0.5 μm. In afurther example, the abrasive grains may have a Moh's hardness of atleast 8 and may include super abrasive grains.

In a further exemplary embodiment, the abrasive article may be formedusing medium to high interface polymer emulsions. For example, anemulsion may be formed of a first liquid component and a second liquidcomponent, the second liquid component being immiscible with the firstliquid component. In this embodiment, the first liquid component forms acontinuous phase surrounding the discontinuous second liquid component.In an example, the first liquid component includes polymeric precursorsand abrasive grains. Once the emulsion is formed, a copolymer derivedfrom the polymer precursors of the first liquid component is furtherpolymerized, such as through radiation curing or thermal curing, to forma polymer matrix in which the abrasive grains are dispersed. In anexample, the polymer precursors are curable through free radicalmechanisms. Depending upon the amount of the first liquid component usedrelative to the second liquid component, the polymer matrix that resultsfrom polymerization of the polymer precursors forms an open cell foamexhibiting a pore and throat configuration.

In a further exemplary embodiment, the abrasive article is used toabrade a surface of a work piece. Here, the abrasive article is formedof a polymer matrix and abrasive grains are dispersed within the polymermatrix. The abrasive article has a void volume of at least 50 vol %. Theabrasive article is contacted with the surface of a work piece, and atleast one of the work piece and the abrasive article is moved relativeto the other. In addition, cooling fluid may be applied to the surfaceof the abrasive article and may flow between the abrasive article andthe work piece. The cooling fluid may be deployed to flow through theabrasive article or swarf may be drawn through the abrasive article.

In an exemplary embodiment, the first and second liquid components areimmiscible in each other. In an example, the first liquid component ishydrophobic, while the second liquid component is hydrophilic or isformed of a water-based solution. Alternatively, the first liquidcomponent may be a water-based solution including hydrophilic polymercomponents, while the second liquid component is an oil-basedhydrophobic component. Alternatively, the first and second liquidcomponents both may be oil-based component that form substantiallyimmiscible phases. In the foregoing examples, the first liquid componentforms a continuous phase of the emulsion and the first liquid componentincludes the polymer precursors that are polymerized to form the solidpolymer matrix.

When forming the emulsion, the first liquid component can be present inan amount of 3% to 50% by volume, such as not greater than about 50% byvolume. For example, the first liquid component can be present in anamount not greater than about 40 vol %, such as not greater than 35 vol%, not greater than about 30 vol %, or even not greater than 25 vol %.On the other hand, the second liquid component can be present in anamount of 50 vol % to 98 vol %, such as at least 50 vol %, at least 60vol %, at least 65 vol %, at least 70 vol %, or even as high as 75 vol %or higher.

In an embodiment, the first liquid component contains polymer precursorsand abrasive grains. In addition, the first liquid component may includeadditives, such as catalytic agents, crosslinking agents, emulsifiers,emulsion stabilizers, coupling agents, or a combination thereof.

The polymer precursor may be a monomer or may be a prepolymer. Forexample, the polymer precursor may include monomers that may polymerizeto form a homopolymer or a copolymer. In another example, the polymerprecursor includes polymer components, such as prepolymers, that includefunctional groups that may be further reacted to form a polymer matrix.In an example, such functional groups react with each other or reactwith chain extenders or crosslinking agents. In a particular example,the polymer precursors include a monomer including at least one doublebond.

In an example, the polymer precursor polymerizes though a radicalpolymerization process. In another example, the polymer precursorpolymerizes through a cationic polymerization process. Further,depending upon the polymeric system and catalytic system used toinitiate the polymerization, the polymeric precursor may be polymerizedusing actinic radiation or thermal treatment.

In particular, the nature of the polymer precursor and other additivesdepends on whether the first liquid component is a hydrophobic orhydrophilic component. In the case in which the first liquid componentforms a hydrophobic phase, the polymer precursors are generallyhydrophobic and exhibit low solubility in aqueous phases.

An example of a polymer precursor useful in a hydrophobic first liquidcomponent includes a monomer having a polymerisable vinyl group, such asmonoalkenyl arene monomers, for example α-methylstyrene,chloromethylstyrene, vinylethylbenzene, or vinyl toluene; an acrylate ormethacrylate ester, for example, 2-ethylhexyl acrylate, n-butylacrylate, isobutyl acrylate, t-butyl acrylate, hexyl acrylate, n-butylmethacrylate, lauryl methacrylate, or isodecyl methacrylate; aconjugated diolefin such as butadiene, isoprene, or piperylene; allenes,for example, allene, methyl allene, or chloroallene; an olefin halide,for example vinyl chloride, vinyl fluoride, or polyfluoro-olefin; or acombination thereof. In a particular example, the polymer precursor isstyrene. In any case, the polymer precursor has a low solubility inwater, and more preferably is insoluble in water. Optionally, the firstliquid component may include two or more polymer precursors, whichmonomers may, for example, be selected from the above list of monomers,and may form a copolymer following the polymerization reaction.

In addition to the polymer precursors, a hydrophobic first liquidcomponent may include a crosslinking agent. An exemplary crosslinkingagent includes a multifunctional unsaturated monomer capable of reactingwith the polymer precursor. Such crosslinking agents may include atleast two functional groups, such as vinyl groups, acrylate groups ormethacrylate groups. The crosslinking agent may include, for example,difunctional unsaturated crosslinking monomers such as divinylbenzene,diethylene glycol dimethacrylate, 1-3-butanediol dimethacrylate, orallyl methacrylate; or tri-, tetra- or penta-functional unsaturatedcrosslinking monomers, such as trimethylolpropane trimethacrylate,pentaerythritol tetramethacrylate, trimethylolpropane triacrylate,pentaerythritol tetra-acrylate, glucose pentaacrylate, glucosediethylmercaptal pentaacrylate, or sorbitan triacrylate; poly-functionalunsaturated crosslinking monomers such as polyacrylates (e.g., sucroseper(meth)acrylate or cellulose(meth)acrylate); or a combination thereof.In a particular example, the crosslinking agent includes divinylbenzene. In another example, the crosslinking agent includes1,4-butanediol dimethacrylate. Further, the relative amount ofcrosslinking agent to the polymer precursor may be in the range of about0.5 wt % to about 70 wt %, such as in a range of about 2 wt % to about40 wt %, or even in a range of about 5 wt % to about 20 wt %, based onthe amount of polymer precursor. In addition, a hydrophobic first liquidcomponent may include an emulsifier.

In addition, the hydrophobic first liquid component may include anemulsion stabilizer. An exemplary stabilizer includes a surfactantsoluble in an oil phase, such as the hydrophobic first liquid component.Suitability of such surfactants may be determined according to thehydrophilic-lipophilic balance (HLB value) of a surfactant. Typically,suitable surfactants have very limited solubility in the internal phase(e.g., the aqueous phase of a water-in-oil emulsion) to adequatelystabilize a high internal phase emulsion and prevent phase inversionoccurring spontaneously. In a particular example, the surfactant mayhave an HLB value in the range of from 2 to 6, such as about 4. Thesurfactant may be non-ionic, cationic, anionic, or amphoteric. Anexample of a surfactant may include a sorbitan fatty acid ester, apolyglycerol fatty acid ester, or a polyoxyethylene fatty acid or ester,or a combination thereof. An example of a sorbitan fatty acid esterincludes sorbitan monolaurate (available as SPAN® 20), sorbitanmonooleate (SPAN® 80), combinations of sorbitan monoleate (SPAN® 80)with sorbitan trioleate (SPAN® 85), or a combination thereof. Anothersuitable surfactant includes “TRIODAN® 20”, which is a polyglycerolester available from Grindsted®, or “EMSORB™ 252”, which is a sorbitansesquioleate available from Henkel®.

In an example, the surfactant is present in the emulsion in an amount ina range of about 1 wt % to about 50 wt %, such as in a range of about 5wt % to about 40 wt %, in a range of about 15 wt % to about 40 wt %, ina range of about 20 wt % to about 35 wt %, or even in a range of about25 wt % to about 33 wt % based on the amount of polymer precursorpresent.

In addition, the first liquid component may include a catalyst orinitiator. Depending upon the reactive nature of the polymer precursor,the catalyst may be a free radical initiator or may be a cationiccatalyst. In addition, the catalyst may be activated through radiationor may be activated through thermal treatment.

Initiation of the polymerization reaction may be accomplished by simplyheating the emulsion comprising a polymerizable monomer composition orby irradiation with UV or other electromagnetic or actinic irradiation.In an example, the initiation of the polymerization reaction comprisesheating the emulsion to form a polymerization initiator species, e.g., afree radical initiator, from an initiator precursor present in theemulsion. An example of an oil soluble initiator includes an azocompound such as azobisisobutyronitrile; a peroxide such as benzoylperoxide, methyl ethyl ketone peroxide, alkylperoxycarbonate such asdi-2-ethylhexyl peroxy-dicarbonate or di(sec-butyl)peroxydicarbonate, oralkyl peroxycarboxylate such as t-butyl peroxyisobutyrate,2,5-dimethyl-2,5-bis(2,3-ethylhexanoylperoxy)hexane, or t-butylperoctoate; or a combination thereof. An exemplary alkylperoxycarbonateis branched at the 1-position and an exemplary alkylperoxycarboxylate isbranched at the α-position or the 1-position.

According to an embodiment, while the polymer precursors are in thehydrophobic first liquid component, the presence of an initiatorprecursor in both the hydrophobic (e.g., oil) phase and the aqueousphase or in the aqueous phase alone may be desirable to ensure morerapid completion of the polymerization reaction. As such, an example ofan initiator precursor includes oil soluble initiator precursors andwater soluble initiator precursors. An example of a water solubleinitiator may include a persulfate such as potassium or sodiumpersulfate, a redox coupler initiator system such as ammonium persulfatetogether with sodium metabisulfite, or a combination thereof. Inparticular, the initiator precursor includes one or more of potassiumpersulfate, AIBN (azobisisobutyronitrile), or a redox couple initiatorsystem comprising, for example, ammonium persulfate and sodiummetabisulfite. The initiator precursor may form part of the oil phase(e.g. AIBN) or the aqueous phase (e.g. potassium persulfate or anaqueous redox coupling system) or both (e.g. AIBN in the oil phase andpotassium persulfate in the aqueous phase).

On the other hand, the first liquid component may be hydrophilic or maybe formed in an aqueous solution. An exemplary polymer precursorincludes hydrophilic functional groups. For example, a polymer componentfor use in a hydrophilic or aqueous first liquid component includesvinyl monomers having unsaturated sulfonic acid groups, for example,acryl amido methyl propane sulfonic acid, allyl sulfonic acid, or acombination thereof. An exemplary vinyl monomer having an unsaturatedamino group is dimethyl aminoethyl methacrylate. An exemplary vinylmonomer having unsaturated carboxyl groups includes, for example,acrylic acid, methacrylic acid, maleic acid, or fumaric acid, andexamples of suitable vinyl monomers having unsaturated carboxylategroups include acrylate, methacrylate, hydroxyethylmethacrylate,diethylaminoethyl methacrylate, hydroxyethylacrylate,diethylaminoethylacrylate, malate, fumarate, methoxypolyethyleneglycolmethacrylate, phenoxypolyethyleneglycol methacrylate, or a combinationthereof.

The polymer precursor may also include a water-soluble salt of anunsaturated carboxylic acid. For example, a water-soluble salt mayinclude alkaline metal salt, alkaline earth metal salt, or ammonium saltof acrylic acid, methacrylic acid, acrylic methacrylic acid, or acombination thereof. Another example of a suitable hydrophilic monomerincludes vinyl pyridines, vinylpyrrolidones, acrylamide, methacrylamide,N-methylmethacrylamide, N-acryloylmorpholine, N-vinyl-N-methacetamide,derivatives thereof, or a combination thereof.

In a particular example, the first liquid component includes the polymerprecursor in an amount in a range of about 0.5 wt % to about 30 wt % ofthe emulsion, such as a range of about 5 wt % to about 20 wt %. In anexample, the polymer precursors include a monomer having at least onedouble bond and a hydrophilic functional group.

In addition, a hydrophilic first liquid component may include acrosslinking agent. In general, the crosslinking agent can be selectedfrom a wide variety of polyfunctional monomers that are hydrophilic orat least partially soluble in the monomer component of the emulsion. Fora crosslinker that is partially soluble in the monomer component, atleast about 50% of the crosslinker dissolved in a 50:50 mixture ofhydrophilic monomer and oil discontinuous phase partitions into thehydrophilic monomer phase when the mixture is allowed to separate intotwo phases.

An exemplary crosslinking agent includes a polyallyl compound, such asN,N′-diallyl acrylamide, diallylamine, diallyl methacrylamide,diallylamine diallylmethacrylamide, diallyl phthalate, diallyl malate,diallyl phosphate, diallyl terephthalate, N,N′-diallyltartardiamide,triallylcitrate, triallyl cyanurate, or triallyl phosphate; a polyvinylcompound, such as divinylbenzene, divinyl sulfone, ethylene glycoldivinylether (e.g., diethylene glycol divinylether),N,N′-methylene-bis-acrylamide, piperazine diacrylamide,N,N′-dihydroxy-ethylene-bis-acrylamide, ethylene glycol acrylate (e.g.,ethylene glycol di-, tri-, or tetra-acrylate), ethylene glycolmethacrylate (e.g., ethylene glycol di-, tri-, or tetra-methacrylate),or glycerin trimethacrylate; a hydroxyvinyl compound, such ashydroxyethylacrylate, or 2-hydroxyethyl methacrylate; an inorganic saltor organic metal salt that generates polyhydric ions such as calcium,magnesium, zinc, or aluminum; or a combination thereof.N,N′-bis-acrylylcystamine and the like are also suitable for use inproducing hydrophilic polymers. A single crosslinker type or a mixtureof types can be employed in the emulsion. In particular, the crosslinkermay be N,N′-methylene-bis-acrylamide, divinyl sulfone, diethylene glycoldivinylether, ethylene glycol diacrylate, or a combination thereof.

In an example, the first liquid component includes the crosslinker in anamount in a range of about 0.005 wt % to about 30 wt % of the emulsion,such as a range of about 1 wt % to about 10 wt %.

Further, the hydrophilic first liquid component may include anemulsifier. An exemplary emulsifier includes a hydrophobic cyclic headgroup and a hydrophilic tail. An exemplary hydrophobic cyclic head groupmay include between about 3 and about 7 carbon atoms and is selected toprovide sufficient rigidity at the hydrophobic end of the molecule toreduce the tendency of the emulsion to reverse (i.e., the tendency ofthe oil discontinuous phase to become the continuous phase). Forexample, the head group may be a cyclic group with multiple hydrophobicgroups, such as, for example, alkyls, cyclic hydrocarbon groups, oraromatic groups, or a combination thereof. Preferably, the head groupdoes not include hydrophilic groups, such as, for example, ionic groupsincluding oxygen, nitrogen, and sulfur. In particular, the head groupconsists of carbon and hydrogen atoms.

An example of an emulsifier includes sugar fatty acid esters, such asdistearate, alkylaryl polyether alcohol, or a combination thereof. In afurther example, an alkylaryl polyether alcohol preparation suitable foruse in producing the hydrophilic polymers has an average number ofethylene oxide units per ether side chain of about 14 or more. Exemplaryemulsifiers are sold under the tradename Triton™ X.

In an example, the first liquid component includes an emulsifier in anamount in a range of about 1 wt % to about 30 wt % of the emulsion, suchas a range of about 1 wt % to about 20 wt %, or even a range of about 1wt % to about 5 wt %.

In addition, the first liquid component may include a stabilizer. Thestabilizer can be a film-forming compound that is soluble in thehydrophilic monomer phase and sufficiently hydrophobic to stabilize theinterface with the oil discontinuous phase of the emulsion. Suitablestabilizers act by forming a continuous film by entanglement ofrelatively strong polymer chains. Stabilizers useful in this regardinclude polymeric film formers for the interface between the hydrophilicmonomer phase of the emulsion and the oil phase(s). An exemplarystabilizer may include a polymer of cellulose derivative, polyacrylate(e.g., polyacrylic acid or polymethacrylic acid), polyalkylene glycol(e.g., polyethylene glycol), partially hydrolyzed polyvinyl alcohol(e.g., PVA less than about 70-80% hydrolysis), another polyol, guar gum,agar gum, or a combination thereof. Also suitable for use as thestabilizer are copolymers of ethylenically unsaturated monomers, such asmalein polybutadiene, malein polyethylene, malein poly α-olefin, or acombination thereof. For example, cellulose derivatives include methylcellulose, hydroxymethyl cellulose, hydroxyethyl cellulose,ethylhydroxyethyl cellulose, hydroxypropyl cellulose, other celluloseethers, cellulose esters, such as cellulose acetate, cellulose butylate,or cellulose acetate butylate, or a combination thereof. In particular,the stabilizer may be methyl cellulose, hydroxyethyl cellulose, PVA, ora combination thereof. In particular, the first liquid component mayinclude a stabilizer in amounts in a range of about 0.001 wt % to about2 wt % of the emulsion, such as a range of about 0.001 wt % to about 1wt %, or even a range of about 0.001 wt % to about 0.7 wt % of theemulsion.

In addition to the polymer precursor, the first liquid component caninclude abrasive grains. Exemplary abrasive grains may include a metalor semi-metal oxide, nitride, or carbide. Alternatively, the abrasivegrains may include an inorganic carbonaceous grain, such as diamond. Anexample of an abrasive grain includes silica, alumina (fused orsintered), zirconia, zirconia/alumina oxides, silicon carbide, garnet,diamond, cubic boron nitride, silicon nitride, ceria, titanium dioxide,titanium diboride, boron carbide, tin oxide, tungsten carbide, titaniumcarbide, iron oxide, chromia, flint, emery, or a combination thereof.For example, the abrasive grains may be selected from a group consistingof silica, alumina, zirconia, silicon carbide, silicon nitride, boronnitride, garnet, diamond, cofused alumina zirconia, ceria, titaniumdiboride, boron carbide, flint, emery, alumina nitride, hardcarbonaceous material, or a blend thereof. Particular embodiments havebeen created by use of dense abrasive grains comprised principally ofα-alumina. In a particular example, the abrasive grains have a Mohshardness of at least 8, such as at least 8.5, or even at least 9. In anexample, the abrasive grains are silicon carbide. In a further example,the abrasive grains may be selected from super abrasive grains, such ashard carbonaceous materials, cubic boron nitride, or any combinationthereof. For example, hard carbonaceous materials include diamond,aggregated diamond nanorods, or any combination thereof. In a particularembodiment, the abrasive grains include diamond. The abrasive grains mayalso have a particular shape. An example of such a shape includes a rod,a triangle, a pyramid, a cone, a solid sphere, or a hollow sphere.Alternatively, the abrasive grain may be randomly shaped. In aparticular example, the abrasive grain has sharp edges or breaks to formsharp edges.

In general, the abrasive grains have an average particle size in a rangeof about 0.1 μm to about 100 μm. For example, the abrasive grains mayhave an average particle size in a range of about 0.1 μm to about 10 μm,such as about 0.1 μm to about 6 μm, about 0.5 μm to about 6 μm, or evenabout 1 μm to about 3 μm. Further, the abrasive grains may have anaverage particle size greater than 500 nm, such as at least about 1 μm.In addition, the abrasive grains may have an average particle size notgreater than about 6 μm, such as not greater than about 3 μm.

The first liquid component may include the abrasive grains in an amountthat results in an abrasive article that includes the abrasive grains ina range of about 2 vol % to about 30 vol % based on the total volume ofthe abrasive article. For example, the resulting abrasive article mayinclude the abrasive grains in an amount of 4 vol % to 26 vol %, such as10 vol % to 25 vol % based on the total volume of the abrasive article.In an example, the first liquid component includes the abrasive grainsin a range of about 5 vol % to about 80 vol %, such as a range of about10 vol % to about 75 vol %, or even a range of about 20 vol % to about60 vol %. In a particular example, the first liquid component includesabrasive grains in an amount that forms at least about 10% by weight ofthe final abrasive article. For example, the final abrasive article mayinclude greater than 10% by weight abrasive grains, such as at leastabout 15% by weight abrasive grains or even as high as about 20% byweight abrasive grains or higher.

In addition, the first liquid component may include a reinforcingfiller. An exemplary reinforcing filler includes silica, zinc oxide,titania, alumina, zirconia, vanadia, chromia, iron oxide, antimonyoxide, tin oxide, other colloidal metal oxides, or a combinationthereof. The reinforcing filler may be included in an amount not greaterthan about 10 wt %, such as not greater than about 5 wt % based on thetotal weight of the abrasive article. In a particular example, thereinforcing filler has an average particle size in a range of 25 nm to500 nm, such as not greater than about 0.5 μm, not greater than about300 nm and in particular, in a range of about 30 nm to about 250 nm.

The abrasive grains or the optional reinforcing filler may be treatedwith a surface treatment or coupling agent to facilitate dispersionwithin the first liquid component. For example, a coupling agent orsurface agent may be included in the first liquid component tofacilitate dispersion of the abrasive grains within that liquidcomponent. In addition, the coupling agent or surface agent may reactwith the polymer precursor to bind the abrasive grains within thepolymer matrix formed from the first liquid component. The nature of thecoupling agent depends upon the nature of the abrasive grain and thenature of the first liquid component and polymer precursors. When thepolymer components include hydrophobic components, the coupling agentmay include a hydrophobic end compatible with or reactive to the polymerprecursors. Alternatively, when the polymer components are hydrophilic,the coupling agent may include the functional groups that are polar andhydrophilic. For example, the polymer precursor reactive groups mayinclude acrylate, methacrylate, hydroxysilane, hydrosilane, epoxy, orvinyl groups, or a combination thereof. Further, the coupling agent mayinclude functional groups configured to react with functional groups ofthe abrasive grains. Particular metal oxides tend to include hydroxidesurface groups which may be reactive with functional groups, such ascarboxylic acids, phosphonic acids, sulfonic acids, or a combinationthereof. Alternatively, the abrasive grain may include an inorganiccarbonaceous compound, such as diamond. The coupling agent may include afunctional group configured to interact with and that may bind to thesurface of the diamond particles.

An exemplary coupling agent includes a silane treatment agent capable ofpolymerizing with a reactive monomer. An example silane treatment agentincludes γ-methacryloxylpropyltrimethoxysilane orγ-glycidoxypropyltrimethoxy silane. Additional surface reagents used tomodify the polarity or hydrophobicity of the abrasive grains include,for example, isooctyl trimethoxysilane, phenyl trimethoxysilane,n-octadecyltrimethoxy silane, 3-cyanopropyl trimethoxysilane,3-aminopropyl trimethoxysilane, or any combination thereof.

A hydrophilic, non-reactive surface treatment agent includes2-[2-(2-methoxy)ethoxy]ethoxy acetic acid (MEEAA),mono(polyethyleneglycol)succinate, mono(polyethyleneglycol)maleate, or acombination thereof. An example of a hydrophilic and reactive acidsuitable for the surface treatment includes2-hydroxymethyl-2-[(N-methacryloxyethyl)carbamoylmethyl]propionic acid(PAMA), mono(acryloxypolyethyleneglycol)succinate,mono(acryloxypolyethyleneglycol)maleate, or a combination thereof.Another suitable reactive acid includes2,2-bis[(N-methacryloxyethyl)carbamoylmethyl]propionic acid (PDMA),acrylic acid, methacrylic acid, β carboxyethylacrylate,mono-2-(methacryloxy)ethyl succinate, or mono-2-(methacryloxy)ethylmaleate. A further acid mixture useful for surface treatment may includealiphatic carboxylic acids, such as, for example, oleic acid, stearicacid, or octanoic acid; aromatic nonreactive acids, such as methoxyphenyl acetic acid or 3,4,5 triethoxy benzoic acid, itaconic acid,toluene sulfonic acid, ethylene glycol methacrylate phosphate; the saltsthereof; or blends thereof.

Depending upon the nature of the first liquid component, the secondliquid component is immiscible with the first liquid component and maybe hydrophobic or hydrophilic. For example, when the first liquidcomponent is hydrophilic, the second liquid component may behydrophobic. An exemplary hydrophobic second liquid component includesoil-based liquids, such as linear or branched alkanes, for example,hexane, octane, decane, dodecane, or a mixture thereof; long chain fattyacids; aromatic hydrocarbons, such as benzene, toluene, xylene, or acombination thereof; ethers, for example, diethyl ether; esters, forexample, ethyl acetate; silicone oils; or a combination thereof.Further, the second liquid component may include an emulsifier or astabilizer.

Alternatively, when the first liquid component is hydrophobic, thesecond liquid component may be an aqueous-based solution or may be anorganic component, such as a polar organic component, that is immisciblewith the first liquid component. For example, the second liquidcomponent may be an aqueous solution, for example, a saline solution; ashort chain alcohol, for example, ethanol, butanol, methanol,isopropanol, propanol, or a combination thereof; glycerol; or a mixturethereof. Further, the second liquid component may include an emulsifieror a stabilizer.

In particular, the second liquid component may be selected based ondielectric constant. For example, when the first liquid component ishydrophilic, the second liquid component may have a dielectric constantless than 15 and when the first liquid component is hydrophobic, thesecond liquid component may have a dielectric constant greater than 15.

In addition, the second liquid component may include a thickening agent.Depending upon the nature of the first liquid component, the thickeningagent may be a cellulous-base thickening agent, a protein-basedthickening agent, an inorganic thickening agent, or a combinationthereof.

In a particular embodiment, the abrasive articles are prepared bycombining polymer precursors and abrasive grains to form the firstliquid component. In addition, catalyst or initiator, crosslinkingagents, coupling agents, emulsifiers, or stabilizing agents may be addedto the first liquid component. The first liquid component is emulsifiedwith a second liquid component that is immiscible with the first liquidcomponent. The second liquid component may also include emulsifiers orstabilizers. The emulsion is treated to facilitate polymerization of thepolymer precursors. For example, the polymer precursors may be curedthrough exposure to radiation or through thermal treatment. Upon curing,the second liquid component is removed. Typically, the resulting polymermatrix with dispersed abrasive grains has an open cell structureexhibiting a pore and throat configuration. For example, FIG. 1 includesan illustration of an open cell structure exhibiting a pore and throatconfiguration. In particular, the open cell structure includesinterconnected pores. The pore and throat configuration is formed whenthe droplets of the second liquid component are located in closeproximity. The polymer matrix forms throats in areas in which the secondliquid component droplets are in close proximity.

In a particular example, the void volume of the abrasive article is in arange of 50 vol % to 98 vol %, such as at least about 50 vol %. Forexample, the void volume of the abrasive article may be at least about60 vol %, such as at least about 65 vol %, at least about 70 vol %, oreven as high as 75 vol % or higher. The void volume is generally notgreater than 98 vol %, such as not greater than 96 vol %. The polymermatrix with the abrasive grains dispersed therein form not greater than50% by volume of the abrasive article, such as not greater than 40%, notgreater than 35%, not greater than 30% or even as little as 25% or lessof the abrasive article.

Further, the abrasive article has a specific surface area of at least2.0 m²/g. For example, the abrasive article may have a specific surfacearea of at least 3.0 m²/g, such as at least 3.5 m²/g.

EXAMPLES Example 1

A sample is prepared that has dispersed diamond abrasive particleswithin the polymer phase. The sample is prepared using an organic phasepolymer and an aqueous internal phase in a ratio of 20:80organic:aqueous. The organic phase is prepared by adding 5 ml ofpoly(ethylene glycol) dimethacrylate (PEGDMA) to 5 ml of styrene in acovet. Titania (<1 μm) wetted with oleic acid is added to the mixture inan amount of 0.3 g and diamond grains (1-2 μm) are added to the mixturein an amount of 0.5 g. The covet containing the mixture is placed in aglass beaker containing ice. The mixture is stirred for 15 minutes at aspeed of 50 RPM.

The mixture from the covet is transferred to a three neck flask. An AIBNinitiator is added to the three neck flask in an amount of 0.15 g. Themixture is stirred for 2 min at 500 RPM.

The aqueous phase is added drop wise to the three neck flask using apipette. The aqueous phase is a solution prepared by adding 10 gCaCl₂.2H₂O to 250 ml of H₂O. After the aqueous phase is added to theflask, the stir speed is increased to 600 RPM. The emulsion is pouredinto a plastic tube and is treated at 70° C. for 24 hours to polymerizethe polymer components.

Example 2

A sample is prepared that has dispersed diamond abrasive within thepolymer phase. The sample is prepared using an organic phase polymer andan aqueous internal phase in a ratio of 40:60 organic:aqueous. Theaqueous phase is prepared by adding 20 g of CaCl₂.2H₂O to 250 ml H₂O.

The organic phase is prepared by adding 4 ml Hypermer, 0.2 g of an AIBNinitiator, and 8 ml styrene to a beaker and is stirred to form a firstmixture. Eight (8) ml poly(ethylene glycol) dimethacrylates (PEGDMA) isadded to a covet with 0.8 g diamond particulate (1-2 μm). The covet isplaced in a glass beaker containing ice and is stirred for 15 min at 50RPM to form a second mixture. The first mixture and the second mixtureare added to a three neck flask and are stirred at 50 RPM. The aqueousphase is added drop wise to the three neck flask using a pipette. Thestir speed is increased to 600 RPM.

The emulsion is poured into a plastic tube and the emulsion is treatedfor 24 hours at 70° C. to polymerize the polymer components.

Example 3

Samples are prepared similar to the method of EXAMPLE 2 using thepolymer components and particulate (<1 μm) specified in TABLE 1 inamounts to form the porosity specified in TABLE 1. The polymercomponents and particulate form an oil phase. The aqueous phasedescribed in relation to EXAMPLE 2 is used in proportion to yield thespecified porosity.

TABLE 1 Sam- Po- ple Polymer Participate rosity 1Polystyrene-co-poly(poly(ethylene glycol) 1 wt % CNT 60 2 dimethacrylate(50/50) 1.9 wt % CNT 60 3 1 wt % SiO₂ 80 4 10 wt % SiO₂ 80 5Polystyrene-co-poly(poly(ethylene glycol) 60 6dimethacrylate-co-methacryloxypropyl 30 wt % SiO₂ 60 trimethoxy silane 7Polystyrene-co-poly(poly(ethylene glycol) 60 8 dimethacrylate (50/50) 809 20 wt % SiO₂ ^(a) 60 10 20 wt % SiO₂ ^(a) 80 11 40 wt % SiO₂ ^(a) 6012 40 wt % SiO₂ ^(a) 80 ^(a)surface grafted with methacryloxypropyltrimethoxysilane (MPS)

Example 4

Samples, including those described above, are tested using the followingmethod to determine wear resistance. In addition, two commercialproducts, denoted BXL6550 and BX623D, available from Saint-GobainCorporation are tested. The samples are aggressively ground with asilicon carbide abrasive paper to evaluate material (weight) loss andlinear loss.

The testing method includes placing a 1.25 in×1.25 in samplecorresponding to EXAMPLE 1, EXAMPLE 2, or samples 1-12 of EXAMPLE 3 inan aluminum sample holder. The sample holder is cleaned, double sidedtape is placed over the surface of the sample holder. The sample isplaced onto the double sided tape and pressed into the sample holder.

A 600 grit silicon carbide paper is placed onto a Struers Rotopol-31rotating table. The aluminum sample holder is placed into a StruersRotoforce—4 rotating head and adjusted to contact the paper. The head isrotated clockwise and the table is rotated counter-clockwise at a speedof 150 RPM. The sample is abraded for 10 seconds with a force of 5 N or10 N.

To determine wear resistance, the weight loss of the sample isdetermined by weighing the sample before and after abrading. Inaddition, the reduction in thickness is measured before and afterabrading.

As illustrated in FIG. 2 and FIG. 3, the wear rate of the sample ofEXAMPLE 2 exhibits weight loss and linear loss on the same order as thatof the BX623D product. Similarly, samples 1, 2, 3, and 4 of EXAMPLE 3exhibit comparable weight loss and linear loss.

Note that not all of the activities described above in the generaldescription or the examples are required, that a portion of a specificactivity may not be required, and that one or more further activitiesmay be performed in addition to those described. Still further, theorder in which activities are listed are not necessarily the order inwhich they are performed.

In the foregoing specification, the concepts have been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope ofinvention.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of features is notnecessarily limited only to those features but may include otherfeatures not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive-or and not to an exclusive-or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

Also, the use of “a” or “an” are employed to describe elements andcomponents described herein. This is done merely for convenience and togive a general sense of the scope of the invention. This descriptionshould be read to include one or at least one and the singular alsoincludes the plural unless it is obvious that it is meant otherwise.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any feature(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature of any or all the claims.

After reading the specification, skilled artisans will appreciated thatcertain features are, for clarity, described herein in the context ofseparate embodiments, may also be provided in combination in a singleembodiment. Conversely, various features that are, for brevity,described in the context of a single embodiment, may also be providedseparately or in any subcombination. Further, references to valuesstated in ranges include each and every value within that range.

What is claimed is:
 1. A method of forming an abrasive article, themethod comprising: combining polymeric precursors including a monomerhaving at least one double bond, and abrasive grains to form a firstliquid component; forming an emulsion from the first liquid componentand a second liquid component, the second liquid component substantiallyimmiscible with the first liquid component; and curing the polymericprecursors of the first liquid component, thereby forming a polymermatrix polymerized from the monomer.
 2. The method of claim 1, furthercomprising treating the abrasive grains with a coupling agent.
 3. Themethod of claim 2, wherein the coupling agent is hydrophobic.
 4. Themethod of claim 1, wherein the polymer precursors are thermally curable.5. The method of claim 1, wherein the polymer precursors arepolymerizable through free radical polymerization.
 6. The method ofclaim 1, wherein the first liquid component is hydrophobic.
 7. Themethod of claim 1, wherein combining the polymer precursors and theabrasive grains includes combining at least 10 wt % of the abrasivegrains.
 8. The method of claim 1, wherein the abrasive grains have anaverage particle size of 0.5 μm to 6 μm.
 9. The method of claim 1,wherein combining the polymer precursors and the abrasive grainsincludes combining an emulsifier with the polymer precursors and theabrasive grains.
 10. The method of claim 1, wherein combining thepolymer precursors and the abrasive grains includes combining astabilizing agent with the polymer precursors and the abrasive grains.11. The method of claim 1, wherein curing comprises exposing theemulsion to actinic radiation or thermal energy.
 12. The method of claim1, wherein forming the emulsion includes forming the emulsion with atleast 65 vol % of the second liquid component.
 13. The method of claim1, wherein the monomer is selected from the group consisting of vinyl,acrylate, methacrylate, conjugated diolefin, allene, and olefin halidemonomers.
 14. The method of claim 1, wherein the polymer matrixpolymerized from the monomer has an open cell structure exhibiting apore and throat configuration.
 15. A method of polishing an article, themethod comprising: applying an abrasive article to the surface of thearticle, the abrasive article comprising a polymer matrix polymerizedfrom a monomer including at least one double bond and abrasive grainsdispersed in the polymer matrix, the abrasive article having a voidvolume of at least 50 vol %; and abrading the surface of the article.16. The method of claim 15, wherein the abrasive article has a voidvolume of at least 65 vol %.
 17. The method of claim 15, wherein theabrasive article includes greater than 10 wt % of the abrasive grains.18. The method of claim 15, wherein the monomer is selected from thegroup consisting of vinyl, acrylate, methacrylate, conjugated diolefin,allene, and olefin halide monomers.
 19. The method of claim 15, whereinthe polymer matrix has an open cell structure exhibiting a pore andthroat configuration.
 20. The method of claim 15, wherein the abrasivegrains have an average particle size of 0.5 μm to 6 μm.